In security systems, passive infrared motion detectors are commonly used to detect intrusion. An example is U.S. Pat. No. 5,077,549 to Hershkovitz et al. co-invented by the present Applicant. Such circuits process a pyrroelectric sensor output signal to generate an alarm signal. In the conventional analog circuits, many active circuit components are used to provide reliable and efficient signal processing.
In the case of Hershkovitz et al., the circuit comprises a band pass amplifier, an absolute value amplifier, a voltage controlled pulse generator, an integrator, a threshold comparator, a timer, logic gates, etc. The number of active elements, such as comparators and logic gates is typically six or more. The band pass amplifier typically has two amplifiers, and the absolute value amplifier typically has a minimum of two amplifiers.
In commercially available high-volume IC components, there is presently available at a low cost IC packages of four comparators/amplifiers (referred to a quad op amp IC's). Packages of five or six op amps are less competitively priced, and it is often desirable to use separate IC's, such as two quads or a quad and a dual op amp to provide enough comparators/amplifiers for the motion detection circuit. Of course, installing an additional component on a circuit board of a motion detector adds to the cost of manufacture.